Classical Variation

With 4. c3 White adds a second guard to d4 and prepares d2-d4, which gains time on the c5-bishop and builds a pawn center. It is the oldest way of treating the Giuoco Piano. Around 1620 Greco chose it consistently while his contemporaries preferred to castle. Lines with an early d4 are sometimes called the Classical Italian. The cost of the move is that the c3-square is no longer available to the queen's knight, so e4 loses its most natural defender.

Black exploits this in more than half of all games with 4...Nf6, attacking e4 at once. The quiet answer 5. d3 reaches the Giuoco Pianissimo, a position that also arises from 4. d3 Nf6 5. c3. It is a slow maneuvering game in the manner of the Ruy Lopez, and Black may contest the center directly with 5...d5. A more aggressive option is 5. b4, Bird's Attack, which chases the bishop and may follow up with Qb3 against f7.

The direct 5. d4, the Center Attack, was the main move for centuries, and Steinitz used it in his world championship matches of 1894 and 1896-97. After 5...exd4 6. cxd4, Black must reply 6...Bb4+. The gambit 7. Nc3 Nxe4 8. O-O gives Black a choice between 8...Nxc3, the Greco Variation, and 8...Bxc3, the Main Line. After 8...Bxc3, 9. d5 is the Moeller-Therkatz (Møller) Attack. It was popular around 1900 but is now regarded as refuted. More modest options at move seven are 7. Bd2 and, in recent practice, 7. Nbd2.

The Modern Line, 5. d4 exd4 6. e5, was popularized by Sveshnikov and has gained ground in the 21st century. Black has to strike back with 6...d5. The usual continuation is 7. Bb5 Ne4 8. cxd4 Bb6. Anderssen often played 8...Bb4+ instead, and Jobava has preferred 7. Be2. White can also gambit with 6. b4, known as the Dubov Italian, or with 6. O-O.

4...d6 is the second most common reply, but it is more passive. After 5. d4 exd4 6. cxd4 Bb6, the La Bourdonnais Variation, White has two center pawns side by side and a clear space advantage. The Closed Variation, 4...Qe7, is a minor sideline. It sets the trap 5. d4 exd4 6. cxd4 Qxe4+, which White avoids by castling first, and the queen can turn out to be badly placed on the e-file. 4...h6 is also seen occasionally. The engine rates the position as roughly level, and in online games White scores slightly better than Black.